Increasing demand for wireless services has made radio spectrum a scarce resource. Even with this scarcity, some wireless networks, characterized by fixed spectrum assignment policies, are inefficient due, in part, to varying demand of licensed bandwidth in terms of time and/or space dimensions. Cognitive radio has emerged as a viable solution to inefficient spectrum utilization. Cognitive radio techniques endow wireless nodes with cognitive capabilities such as the ability to sense an electromagnetic environment, make short term predictions, and react by adapting transmission parameters (e.g., operating spectrum, modulation, transmission power, etc.) to improve utilization of available resources.
Typical cognitive radio applications to spectrum sharing involve a hierarchical access structure which distinguishes between primary users (e.g., users of licensed spectrum or legacy spectrum holders) and secondary users (e.g., users who access licensed spectrum dynamically without inducing intolerable Quality of Service (QoS) degradation on primary users). For instance, such scenarios involve concurrent communications of cognitive users (e.g., secondary users) competing over physical resources made available by primary users. From a signal processing perspective, secondary users transmit over multi-dimensional space, with coordinates representing time slots, frequency bins, and/or angles, with the objective of identifying a transmission strategy exploring available degrees of freedom while inducing no interference or limited interference on primary users.
One approach to implementing such opportunistic communications is to utilize global techniques. A central node can compute transmission strategies for wireless node with the objective of achieving a greater system-wide information rate. Such techniques often apply a theory of cooperative games (e.g., Nash bargaining optimality criterion); however, such techniques can often fail to control an amount of aggregate interference generated while also being computationally expensive. In addition, the central node, for best results, relies upon knowledge of channels and interference structures at every receiver, which can introduce scalability concerns and increased overhead (e.g., increased signaling among nodes).
The above-described deficiencies of conventional wireless networks and spectrum sharing techniques are merely intended to provide an overview of some of the problems of conventional systems and techniques, and are not intended to be exhaustive. Other problems with conventional systems and techniques, and corresponding benefits of the various non-limiting embodiments described herein may become further apparent upon review of the following description.